Synthesis gas, hydrogen and carbon monoxide, is used in a variety of hydrocarbon synthesis processes, e.g., Fischer-Tropsch. However, trace components that find their way into the synthesis gas are often poisons for hydrocarbon synthesis catalysts. An example of a trace component that poisons Fischer-Tropsch catalysts is hydrogen cyanide. This component is difficult to remove from synthesis gas because of its low solubility in common solvents, e.g., water, and because of its low concentration, usually less than about 100 ppm, removal by adsorption is difficult. Also, chemical removal by, for example, alkaline scrubbing, is hampered by the presence of other acidic materials, e.g., CO.sub.2. Consequently, a need exists for the economic removal of HCN from synthesis gas at levels of at least about 95%, and particularly at temperatures similar to those employed in the hydrocarbon synthesis step.